The present invention relates to an apparatus and method for erasing data recorded on a magnetic disk, and more particularly to an apparatus and a method for erasing magnetic disk data by making use of an external magnetic field.
A typical hard disk drive includes a magnetic disk, a spindle motor for rotating the magnetic disk, and a magnetic head for writing data onto and reading data from the magnetic disk. The hard disk drive is provided with an enclosure case, which houses components. The enclosure case generally includes a box-type base, which has an opening, and a plate-like top cover, which covers the opening in the base.
The hard disk drive is completely assembled by placing the components within the base and installing the top cover over the opening in the base. After completion of assembly, a servo pattern is written onto the magnetic disk. After completion of a servo pattern write, the hard disk drive is subjected to various tests prior to product shipment. If the hard disk drive is found to be defective, parts irrelevant to a defect are collected after hard disk drive disassembly and reused. When the magnetic disk is to be reused, it is necessary to erase the written servo pattern for the purpose of avoiding the interference with a new servo pattern that will be written for a new product. If the written servo pattern is found to be defective, it is also necessary to erase such a servo pattern. Further, test data is written on the magnetic disk for testing prior to product shipment. Therefore, it is also necessary to erase the test data from a hard disk drive that is found to be defective.
In recent years, data erasure is also an important concern for hard disk drives that are to be discarded due, for instance, to a defect. When, for instance, the aforementioned spindle motor or magnetic head becomes defective, the information stored on the hard disk drive cannot be read by performing a normal procedure. As a result, it is found that the hard disk drive is defective. However, the magnetic disk still stores information, which could be read by using an appropriate apparatus and method. Therefore, the defective hard disk drive should not be discarded as is from the viewpoint of information protection. It is preferred that the defective hard disk drive be discarded after completely erasing the information recorded on the magnetic disk.
A conventional method used to solve the above problem is to make the information stored on the magnetic disk in the defective hard disk drive unreadable by physically damaging the defective hard disk drive before it is discarded. From the viewpoint of parts recycling and garbage separation, however, the hard disk drive should not be physically damaged for disposal purposes. Even when only the magnetic disk is to be physically damaged, it is necessary to remove the magnetic disk from the housing. Thus, this conventional method does not work efficiently when a large amount of hard disk drive data is to be erased.
An apparatus capable of erasing data recorded on a magnetic disk while it is mounted in a hard disk drive is disclosed by Patent Document 1 (International Publication No. WO98/49674). This apparatus includes two upper permanent magnets, which are positioned adjacent to each other to attract each other, and two lower permanent magnets, which are positioned adjacent to each other to attract each other. The permanent magnet surfaces that vertically face each other have the same polarity.
When the magnetic disk rotates within a magnetic field, the magnetic field parallel to the entire magnetic disk surface works so as to erase the data. An external magnetic field, which is generated by the permanent magnets, makes it possible to rapidly erase the data from the magnetic disk. However, this method requires an apparatus that rotates the magnetic disk. Further, if the spindle motor for the hard disk drive whose data is to be erased is defective, the magnetic disk cannot be rotated. If the magnetic disk is rotated by a rotation mechanism for a data erasure apparatus and without using the spindle motor of the hard disk drive, the number of steps to be performed increases to the detriment of efficiency (e.g., it is necessary to perform the steps for removing the hard disk drive top cover and removing the magnetic disk from the hard disk drive).
An apparatus for erasing data from a magnetic disk without rotating it is disclosed by Patent Document 2 (Japanese Patent JP-A No. 110908/2004). This apparatus moves a hard disk drive relatively in relation to a data erasure permanent magnet. Data erasure is achieved by moving the magnetic disk of the hard disk drive in such a manner that the entire surface of the magnetic disk passes over the permanent magnet.